For me the easiest tell is the up front, unprompted, and unsolicited declaration of nonpoliticalness. When someone takes the time and expends the breath to announce how nonpolitical they are, what follows is almost always a rant about how everything/everyone else is too political these days, and that of course leads into something between status quo advocacy and outright reactionary/regressive sentiments for some fabled time before those wicked politics were visible to the nonpolitical ranter. 
People that are hostile to service workers. Some just want to take some ideological stand against tipping when the service worker doesn't really have a choice and needs those tips to survive in the current unjust system in a way where ideological purity gestures toward that service worker just look like being a greedy and sanctimonious asshole. The worst of such people will actually declare, shamelessly, that they believe that service workers don't deserve a living wage. The implications of that are 
worthy.
I may get shit for this, but I'll say it anyway: this hair and beard combo, seen on living people. 
I have yet to meet anyone in person with that look that wasn't a chud.
(If one of you is a comrade with that look, I am sorry in advance for the prejudice and if I ever meet you in person I will atone by buying you a drink or something.)
A fash dude in person tried to get into a group I was organizing with. We went on a day there, day back roadtrip with him before we really knew him and by the end of it we cut him out completely.
Two biggest red flags were:
It didn't take long for the full fash ideology to be on display and as soon as we dropped him off we blocked him on everything and never looked back.
Or they are fear mongering with the intent to sway opinion that societal collapse is imminent so that we all must be ready to use extreme measures.
"Societal collapse" in their mind is the collapse of their privileged life. "Extreme measures" meaning find ways to quietly genocide a group of people before it becomes an open power struggle.
finding
looting
Always love to walk through that logic. Why do hungry people have a higher likelihood of murdering each other? Is it 9 missed meals for an individual or does a group of people need to experience those missed meals collectively? How long can people get by on 2 meals a day without being murdered? How long can people get by on 1 meal a day without being murder? 1 meal every 2 days? What if they’re skipping meals but their kids are fed? If it takes 3 days to reach Murdertown, what happens on days 1 and 2? Is everyone dead on day 4? Are there particular people who tend to be targets of the murder? Is the murder for meat? Is it out of anger? Is a power play? How do you prepare for The Purge But For Real? What should we do to prevent it? What can we do? Why do you think about this so often? Do you think it’s imminent? Why why why why why
I imagine the argument is that they're murdering each other over the remaining scraps of food. Which doesn't seem entirely untrue considering how many wars have historically been fought over farmland and resources.
That being said the idea of most people turning into murderers doesnt seem to fit too well into what happened during actual famines.
I lived in one of the wealthiest places in America during that time. One if the poorest spots in America was two towns over.
"how do you do fellow leftists? hey just so you know, i'm racist. hope that won't be a problem"
On the first part shouldn't the solution be making sure everyone has what they need to avoid people being in desperate straights? It seems more sensible to do this than try to beat everyone into submission
His mindset was that it's going to happen anyway because Western decline, and we are going to have to defend against immigrants, past and present.
Why not just prepare to accept new immigrants and focus on making a stronger society? We will never be able to handle climate collapse otherwise.